One animal’s waste, another animal’s war
Of course, fertilizers did exist before the advent of synthetically produced nitrogen. Both crushed animal bones and excrement have been used for centuries, as they contain potassium nitrate, a naturally occurring nitrogen-rich substance capable of providing the needed substance to crops. Often called saltpeter, this substance’s value increased exponentially when repurposed for a new role in warfare.
Gunpowder, first produced in China, arrived in Europe in the late 13th century and quickly became a defensive necessity for the continent’s warring fiefdoms. While charcoal gives gunpowder its characteristic black color, the active ingredient in animal bones and excrement, saltpeter, gives gunpowder its all-important pop. Chemically a mystery at the time, saltpeter’s dual use for growing crops and blowing open castle gates was understandably hard to ignore. So much so, in fact, that King Charles I of England ordered his subjects to collect their urine with the purpose of creating nitrate beds for future small-scale saltpeter mining.
By the 18th century, domestic production of saltpeter could neither meet the military aspirations of most European empires nor their subjects’ rapidly multiplying stomachs. Conversely, innovations in transport, especially across previously unnavigable seas, made conquering new lands and obtaining new resources increasingly possible. Within decades, both saltpeter mines in Chile and deposits of guano, the nitrogen-rich excrement of birds and bats, in Peru became key sources of fertilizer and gunpowder for Europe, setting the stage for a prolonged period of jockeying for their control.
The first, aptly called the Guano War, was fought in the 1860s between Spain and its former colonies Peru and Chile. The war was sparked by Spain’s seizure of the Chincha Islands—whose guano deposits the Peruvian government sold to pay all of its outstanding debts. Peru’s robust counter forced the Spanish fleet to circumnavigate the world in retreat, a decisive victory for the former colonies. Less than 15 years later, however, the South American countries were again quarreling over resources, but this time among themselves. From 1879 to 1883, the Saltpeter War pitted Peru and Bolivia against Chile for control over the lifeless Atacama Desert, both to better establish the region’s borders and to gain access to the world’s largest-known reserves of saltpeter nitrates. Emerging victorious, Chile seized key pieces of infrastructure, such as the region’s main nitrate-transporting railroad, which would go on to form the basis of the country’s economy; between the mid-1880s and the mid-1890’s, export taxes on nitrates received by the Chilean Government jumped from 43 to 68 percent of its total revenue.
The immense value of these exports, of course, came from the growing prosperity—and subsequent arms race—of 19th century European empires. However, like the other sources of nitrogen before it, guano could not meet all of the demands of a rapidly industrializing world. By the 1880s, the majority of guano on the Chincha Islands had been excavated—about 20 million tonnes in 40 years—causing empires to rely almost entirely on Chile’s deposits of saltpeter. Moreover, the breakneck growth and militarization of Europe, coupled with dwindling supplies of essential resources, suggested that further conflict was not a question of if, but when.
Fixing nitrogen to break enemies
With the diverse uses and dwindling supplies of both guano and saltpeter in mind, European scientists raced to secure more reliable sources of nitrogen compounds. Countless numbers of the continent’s premier scientists tried their hands at solving the elusive riddle of artificial ammonia production. Some, such as Wilhelm Ostwald, were flat out incorrect in their findings, while others, including Kristian Birkeland, simply could not find an efficient-enough solution. Regardless, attempts came closer to success each year, and the looming shadow of war ensured that these efforts did not go fiscally unrewarded.
For Germany especially, additional sources of ammonia were crucial. Only unified in 1871, Germany’s young government at times struggled to feed its rapidly growing population. Compounded by the country’s relatively poor soils and lack of significant empire compared to its rivals, Germany was forced to import increasingly burdensome amounts of Chilean saltpeter. Between just 1900 and 1912, Germany’s saltpeter imports jumped from 350,000 tonnes to nearly 900,000 tonnes. The United States, with a population roughly 30 percent larger than Germany’s at the time, consumed only about half as much saltpeter. Meanwhile, from 1908 to 1913, military spending among major European powers increased by roughly 50 percent, further exacerbating Germany’s self-perceived vulnerabilities. Germany needed nitrogen for both fertilizer and weapons, though its imported supply from Chile was becoming precarious. Increasingly consumed by an intensifying arms race with the United Kingdom, yet lacking the vast and diverse empire of its maritime rival, Germany rested its hopes on a solution from within.
Thus, when a German chemist named Fritz Haber successfully derived ammonia from the essentially limitless inert nitrogen in the earth’s atmosphere, his rapidly militarizing homeland quickly took notice. Yet Haber’s first experiments were more a triumph of theory rather than of practice. In 1909, Haber could still only produce modest quantities of ammonia, or just 125 milliliters an hour. By the outbreak of World War I, Germany still needed to import Chilean saltpeter to meet demand. Unsurprisingly, the British moved quickly to cut off Germany’s access to the vital saltpeter deposits in Chile. Half a world away and defended by the world’s largest navy, Chilean saltpeter was no longer an option for Germany over the remainder of the war. But soon it wouldn’t matter. Haber had already cracked the code, and it was only a matter of time before Germany figured out how to scale up production.
The technology available for industrial production had been available as early as 1913, developed by a research team led by a scientist named Carl Bosch from chemical giant BASF. But it would take years before Germany could produce enough ammonia to make up for lost saltpeter imports after the British navy cut off supply. Over the next four years of war, the German government would go on to spend a staggering $100 million—the equivalent of $2.4 billion today—to develop and construct nitrogen fixation plants. German agriculture would see some benefits, but with all efforts pointed toward the war, major innovation in producing nitrogen fertilizer would have to wait. Although by dubious means, these investments in the so-called Haber-Bosch process helped Germany fuel its explosives, feed its people, and extend the length of the war by over a year.
Haber’s invention would also infamously contribute to the war effort through military uses other than explosives. On the war’s notorious western front, advances by both sides had stalled, and casualties continued to mount. Frustrated by the impasse, the German government granted use of chlorine gas, a weapon that would have been impossible to produce without the Haber-Bosch process. Although casualties from the gas itself were relatively limited, its application represented a new and horrifying chapter in both chemical and psychological warfare. Instrumental to the production of ammonia—and therein poison gas, explosives, and the Central Powers’ food supply—Ludwigshafen, Germany, the home to BASF’s plants, also earned the dubious distinction in 1915 of being the target of one of the world’s first strategic aerial bombardment, again signaling the vital and enmeshed nature of nitrogen-fixation and its uses.
After the end of World War I, large-scale efforts to use the Haber-Bosch process for agricultural purposes became the priority. Luckily for the rebuilding effort, the transition from explosives to agricultural uses was relatively simple, as ammonia, which is gaseous at room temperature, can easily be turned into salts and solutions. Soon enough, British and American efforts to produce ammonia using the Haber-Bosch process were also successful. But while significant improvements were made in the interwar period, it was not until World War II, which would demand even more ammonia for explosives, that ammonia production modernized enough to impact agriculture on a mass scale.
The nitrogen cycle, its science, and the world’s supply
From a scientific perspective, it should come as no surprise that Haber also sowed the seeds of an agricultural revolution. Haber’s process of nitrogen fixation uniquely mimics the soil’s organic process for obtaining nitrogen.
Intrinsically, bacteria often form symbiotic relationships with plants by which they convert atmospheric nitrogen, a stable and unreactive composition, into ammonia, a stable but reactive form of nitrogen. Lightning strikes can also provide another source of nitrogen for the soil as their force converts atmospheric nitrogen into nitric acid. This usable supply of nitrogen allows plants to undergo photosynthesis, grow larger, and become more fertile. Excess ammonia that plants don’t use is returned to the atmosphere by bacteria through a process called denitrification.
Using 450 °C heat, pressure 200 times greater than that of our atmosphere, and a metal catalyst, Haber was able to use abundant but inert atmospheric nitrogen (N2) and hydrogen (H2) to produce ammonia (NH3), bypassing the slow and less efficient natural process.
The Haber-Bosch process supplants this natural exchange of nitrogen between air and soil by tapping into the unlimited supply of nitrogen in the atmosphere. The process is more akin to a lightning strike than bacterial symbiosis, as it requires 200 atmospheres of pressure, 450 degrees Celsius of heat, and an iron catalyst to create the necessary conditions to produce ammonia. In the 1950s, farmers shunted pressurized containers of gaseous ammonia into the ground, providing an injection of nitrogen into the soil that allowed for previously unprecedented plant growth. Ammonia was eventually used to create other nitrogen compounds that act as fertilizers, including urea, a dry substance, which can more easily be mixed with other vital nutrients for plant growth, namely potassium and phosphorous. However, the general principle of enriching, and often over enriching, soil with nitrogen has remained the same since the invention of the Haber-Bosch process.
Unsurprisingly, crop yields from the 1950s onward grew exponentially. Along with improved seed varieties, artificial pesticides and better irrigation techniques, wide use of nitrogen fertilizers played a major role in what became known as the Green Revolution, the staggering jump in crop yields in developed countries in the mid-20th century thanks to new technologies. Corn yields in the United States, for example, which rarely reached 30 bushels per acre before 1940, were suddenly above 40 bushels per acre in the 1950s and eventually hit triple digits in 1978/79 with a 101 bushel-per-acre harvest. While other improvements like seeds and pesticides continue to make larger strides today in terms of improvement, nitrogen fertilizers remain crucial. The Nitrogen in Europe Assessment, published in 2011, estimates that, without nitrogen fertilizer, the EU-27 would only produce 86 million tons of wheat on average instead of 150. Since 1950, the world’s population has grown by 168 percent, with increased yields indubitably supporting this rapid population growth.
Given the revolutionary effects of the Haber-Bosch process, it may come as a surprise that a growing chorus of scientists and governments are warning of a future in which humans continue to use nitrogenous fertilizers at the rate we do today. Further, like the nitrogen stored on the Chincha Islands, production of nitrogen via the Haber process cannot sustainably feed an ever growing population.
A not-so-fertile future?
Haber’s invention may have solved the issue of supply, but new constraints have since arisen as the intensive use of nitrogen on farms proves to be increasingly detrimental to the environment. Thirty to 50 percent of nitrogen injected into the ground is unused by crops and instead ends up as runoff, causing excessive growth of plants in lakes and streams. In these so called dead zones, the excessive plant growth suffocates all aquatic life underneath; currently, a dead zone the size of Connecticut exists in the Gulf of Mexico due to runoff from Midwestern farms that enters the gulf from the Mississippi River.
Excessive nitrogen similarly destroys the atmosphere. Nitrous oxide, a product of nitrogen fertilizers, is 300 times more effective at trapping heat than carbon dioxide and has contributed to the resurgence of acid rain in developed countries such as the United States. These globalized effects of nitrogen pollution offer no easy solution, especially considering the essential role that artificial fertilizers play in feeding the population. Most searingly, recent research indicates that synthetic nitrogen destroys the soil over the long term by decreasing its ability to retain water and increasing its dependency on artificial nitrogen sources.
While a combination of government action and technological innovation will be necessary to overcome this environmental hazard, applying solutions such as using genetically modified crops and precision agriculture techniques to efficiently use nitrogen will be difficult in those countries that need it the most.
To innovation, and beyond
To combat the inherent limits of fertilizers, such as the acute environmental risks associated with excess use, numerous innovations have been made in recent decades. Chiefly, drones have been increasingly used for agricultural purposes as the precision agriculture industry continues to flourish. In fact, the Association for Unmanned Vehicle Systems International (AUVSI) projects that more than 80 percent of the drone market will target agricultural uses in the next 10 years. Also first developed around the time of World War I, unmanned aerial vehicles (UAVs) have been used by the military since the late 20th century to coordinate attacks and provide constant aerial imagery of areas too dangerous for manned planes to fly over. As drones too have evolved over the past century, current iterations are now small and cheap enough for relatively unrestricted public use. Based on the tenets of efficiency, drones, coupled with various analytics software, allow farmers to better assess the health of their crops and therefore more efficiently use both water and fertilizers. Fittingly, drones, like synthetic ammonia, were also first developed for the military.
Recent studies have also highlighted the exciting prospects of controlled-release fertilizers, for compounds such as urea, rather than the method of indiscriminate spraying commonly used today. As mentioned previously, less than half of nitrogen applied is absorbed by plants, and the remainder contributes to a host of other environmental imbalances. By incorporating slow-release fertilizers, plants are able to absorb more nutrients, farmers need apply less fertilizer, and ecosystem damage is reduced. In corn, for example, deep application of controlled-release urea increases water use efficiency, net income, and yields by 3.2, 4.2 and 6.5 percent, respectively.
Although innovations in corn production helped satiate growing demand for a time, US yields haven’t grown as quickly as domestic consumption.
Genetically modified (GM) varieties designed to boost yields also offered some promise initially, but their efficacy is uncertain. For one, some countries that could benefit from higher yields, including India, have been hostile to the introduction of GM crops. And new research suggests that adoption might not even be the solution. A May 2016 report from the National Academy of Sciences concluded that GM varieties have not significantly increased the rate at which yields for major crops were already increasing
Looking ahead, China, Brazil, and India pose the greatest problem in lowering the world’s nitrogen use. While countries such as the United States have the organizational capacity and capital to invest in the measures necessary to curb nitrogen pollution, less-developed countries are not necessarily capable of implementing efficient farming techniques.
China, the largest consumer of synthetic nitrogen, provides a useful and terrifying use case for the difficulty of limiting nitrogen fertilizers in developing countries. Food security is a paramount issue on both an individual and bureaucratic level for China and its people. Many Chinese citizens grew up in the wake of the country’s Great Famine and now supremely value their abundant food supply. The Chinese government has similarly placed a high priority on food security for its people. This priority has led to heavy nitrogen subsidies that allow 22 percent of the world's population to be fed on 7 percent of the world’s arable land. In some cases, researchers have found that Chinese farmers could use two-thirds less nitrogen fertilizer and receive the same or better results when growing staples like corn or rice. While officials have begun to tackle the environment disasters that have already taken China, organizing the means to ensure more responsible nitrogen use is difficult in a farming society that is still largely decentralized; most farmers still own only an acre of land and the government hasn’t been able to create a “coherent management strategy of policy” to take on excessive nitrogen use.
There are clear environmental and food security threats from nitrogen fertilizer overuse, especially in agricultural practices. But can the world actually mobilize to reverse this trend? If history is to act as a guide, the next leap forward for agriculture may only follow one in warfare. It’s not difficult to imagine that a period of extreme conflict could ultimately precipitate the innovations needed to prosper in the future, not unlike the Haber-Bosch process and World War I. Hopefully, the growing threat of diminishing resources will be enough to catalyze change.
Of course, it is difficult to predict the trajectory that the effects of technological innovations will have on global society. What is clear, however, is that rather than representing distinct and mutually exclusive chapters of human history, agriculture and warfare are often engendered by the same innovative and disruptive technological forces. BASF—the first company to manufacture ammonia using the Haber process and now one of the largest fertilizer producers in the world—offers a prime example of the link between military and agricultural innovation. In other words, while our military innovations have fueled agricultural productivity and prosperity on previously unseen levels, it may be our agricultural innovations that ultimately divert us from a potential future of war.